Generally speaking, large facilities, such as university campuses or military bases, rely on an exterior sound system for broadcasting alerts and/or messages. For example, during a time of emergency the sound system may broadcast an alert tone to indicate the instance of an emergency or an emergency type. The alert tone is often followed by a voice announcement, which can include important instructions and/or announcements. The announcements broadcast are not limited to emergencies, however, and can be used in almost any scenario.
The sound system typically includes multiple speaker units (i.e. loudspeakers, speakers, speaker sources) that are installed outside and around the facility on poles, on tops of buildings, or on sides of buildings. The speaker units may receive audio signals (i.e., messages) via wires or wirelessly via radio waves.
Because the speaker units are typically positioned at a relatively low height (with respect to obstructions) and are typically oriented to project audio in a horizontal direction aligned with the ground, listeners may find the broadcasted audio messages intelligible in certain circumstances.
For example, the power (i.e., sound pressure level) of the speaker unit may be adjusted to avoid harming users that are proximate to the speaker unit. As a result, a listener that is located at a large distance from a speaker unit may not be able to hear the announcement.
To accommodate more listeners, more speaker units may be added to the facility. However, multiple speaker units can produce overlapping audio in an area. The overlapping audio is comprised of replica audio signals that are delayed relative to each other. As a result, a listener may not be able to understand the announcement.
Buildings in the facility may block audio from being received in areas (i.e., shadow regions) or may produce echoes caused by reflections that reduce intelligibility due to the overlapping audio described previously.
Time delays may be applied to speakers in a system to mitigate the overlapping audio for a particular area, but this is not effective for wide area broadcasting and requires customization that is not suitable for portable or temporary sound systems.
Often sound systems are needed on an ad hoc basis. For example, a natural disaster, an act of terrorism, a power/communication outage, or any other disruption in normalcy may require a sound system to broadcast important messages quickly to a wide area. In addition, there may be commercial and/or public service scenarios that are not life threatening but could also benefit from ad hoc broadcasting of audio messages.
Existing portable sound systems typically include a movable base station that includes a mast with one or more speakers affixed to an end opposite to the base station. The mast may be extended to a height and rotated to provide broadcasting coverage for an area. These portable sound systems suffer, however, from the drawbacks listed above because of the limited height of the mast. Additionally these portable systems may be difficult to quickly arrange and coordinate into the collection of sound systems necessary to provide intelligible audio messages for a wide area.
A need, therefore, exists for a sound system that is capable of broadcasting intelligible audio messages to a wide area without the need for fine-tuning or customized hardware/software and that is capable of being moved, deployed, and stored quickly.